INTRODUCTION Disc degeneration (DD) on magnetic resonance imaging (MRI) has been noticed in children under the age of 10 years (1). A pooled prevalence of DD on MRI in 44% and 22% of adolescents with and without low back pain (LBP), respectively, has been established (2). Increasing occurrence of LBP after puberty has been explained at least partly by the growth spurt (3,4). Linear growth during puberty has been suggested as an independent risk factor for development of spinal pain (4). In this longitudinal cohort study, we wanted to assess the effect of growth between the ages of 11 and 18 on the discs of the lumbar spine.
METHODS Ninety-four (94) 8-year-old healthy schoolchildren took part in this longitudinal study with a follow-up at ages 11 (N=81) and 18 (N=71). The study comprised of a semi-structured interview, a clinical examination and a lumbar spine MRI at all time points. The participants’ height and sitting height were measured with a stadiometer and weight with a balance-beam scale. We defined Body Mass Index (BMI) at age 11 using the ISO-BMI formula, at age 18 we used the standard formula for adults. Body Surface Area (BSA) was calculated using the Mosteller formula. The change in BSA between age 11 and age 18 was analyzed by tertiles, for all the other measures we used the percentage of growth. We assessed the lumbar discs (L1-S1) on the mid-sagittal T2-weighted MRIs using the Pfirrmann classification. The association of Pfirrmann grade 3 or higher at any lumbar level to relative growth was analyzed.
RESULTS We report the results of those 59 participants who had MRI performed at both 11 and 18 years of age. In the highest tertile of increase in BSA (>43%), 76% of participants had at least one disc with a Pfirrmann grade 3 or higher at age 18 years, while only 10 to 21% of participants in the other tertiles had DD. Sex- and baseline-adjusted OR for DD for every additional 10% increase in BSA was 1.08 (1.02 to 1.15). Sex- and baseline-adjusted OR (95% CI) for DD was 10.5 (1.60 to 68.7) and 7.92 (1.19 to 52.72) with every additional 10% increase in height and sitting height, respectively. For every 10% additional increase in weight the adjusted OR for DD was 1.51 (1.12 to 2.04) and for BMI 1.05 (1.01 to 1.09).
DISCUSSION Our study design enabled us to examine the effect of growth on the lumbar discs. In this small group of healthy adolescents, greater relative increase in bodily measures during the pubertal growth spurt was associated with more severe DD in early adulthood. As height and sitting height cannot be influenced, avoiding excess weight gain during puberty seems to be beneficial for the health of the lumbar discs.